Stabilizing mixture of 4, 4&#39;-diaminodiphenyl ether and 2, 4&#39;-diaminodiphenyl ether



STABILIZING MIXTURE OF 4,4'-DIAMINODI- PHENYL ETHER AND 2,4-DIAMINODI-PHENYL ETHER Henryk A. Cyba, (Illicago, IIL, assignor, by mesneassignments, to Universal Oil Products Company, Des Plaines, 111., acorporation of Delaware No Drawing. Filed Mar. 7, 1958, Ser. No. 719,762

3 Claims. (Cl. 252-403) This invention relates to the stabilization oflubricants by incorporating therein a novel synergistic inhibitorcomposition of exceptionally high potency.

As will be shown by the examples appended to the present specification,thenovel inhibitor composition of the present invention possesses a highdegree of effectiveness far beyond that obtained through the use of eachof the components singly. The synergistic effect obtained through theuse of both of the components of the composition is truly unexpectedbecause, as will be subsequently described in detail, the individualcomponents are of sim ilar chemical constitution and would not beexpected to exert a synergistic effect. Furthermore, this synergisticeffect appears to be peculiarly adapted to specific substrates. The datain the examples of the present application will show exceptionally highsynergistic effects in lubricants. On the other hand, no suchsynergistic effect was observed in other substrates such as gasoline,rubber and fatty material.

The lubricants which are stabilized in accordance with the presentinvention are either solid or liquid and are obtained from any suitablesource, generally being either of synthetic or petroleum origin. Inrecent years stringent requirements have been established for lubricantsin certain applications including, for example, winter grade crank caseoils, turbine engine oils, aviation instruments, automatic weapons, etc.For example, aircraft gas turbines require oils capable of providingsatisfactory lubrication at temperatures ranging as low as 65 F. and ashigh as 275 F. during use. Temperatures up to 500 F. are encountered forintervals of from one to two hours during shutdown. It is apparent thatthese lubricants must possess high stability. Other lubricants also areconsiderably improved through the use of the novel synergistic mixtureof the present invention.

As hereinbefore set forth, the lubricants may be solid and thus areincluded under the classification of grease. These may be either ofsynthetic or petroleum origin. The synthetic greases generally arereferred to as lithium base grease, sodium base grease, calcium basegrease, barium base grease, strontium base grease, aluminum vbasegrease, mixed base greases, as barium-calcium, barium-lithium, etc.These greases are solid or semi-solid gels and, in general, are preparedby the addition to mineral or synthetic oils of hydrocarbon-solublemetal soaps or salts of higher fatty acids as, for example, lithiumstearate, calcium stearate, aluminum naphthenate, etc. The grease maycontain thickening agents such as silica, carbon black, talc, organicmodified bentonite, etc., polyacrylates, amides, polyamides, aryl ureas,methyl N-n-octadecyl terephthalomate, etc. Another type of grease isprepared from oxidized petroleum wax, to which the saponifiable base iscombined with the proper amount of the desired saponifying agent, andthe resultant mixture processed to produce a grease. Other types ofgreases in which the features of the present invention are usableinclude petror leum grease, Whale grease, wool grease, etc., and'thosemade from inedible fats, tallow, butchers waste, etc.

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The lubricating oils may be of synthetic or petroleum origin. Thesynthetic lubricating oils are of various types including aliphaticesters, polyalkylene oxides, silicones, esters of phosphoric and silicicacids, highly fluorine-substituted hydrocarbons, etc. Of the aliphaticesters, di-(2- ethylhexyl) sebacate is being used on a comparativelylarge commercial scale. Other aliphatic esters include dialkyl azelates,dialkyl suberates, dialkyl pimelates, dialkyl adipates, dialkylglutarates, etc. Specific examples of these esters include dihexylazelate, di-(Z-ethylhexyl) azelate, di-3,5,5-trimethylhexyl glutarate,di-3,5,5-trimethylpentyl glutarate, di-(2-ethylhexyl)pimelate,di-(Z-ethylhexyl) adipate, triamyl tricarballylate, pentaerythritoltetracaproate, dipropylene glycol dipelargonate,1,5-pentanediol-di-(Z-ethylhexanonate), etc. The polyalkaline oxides andderivatives include polyisopropylene oxide, polyisopropylene oxidediether, polyisopropylene oxide diester, etc. The silicones includemethyl silicone, methylphenyl silicone, etc., and the silicates include,for example, tetraisooctyl silicate, etc. The highly fluorinatedhydrocarbons include fluorinated oil, perfluorohydrocarbons, etc.

The lubricating oils of petroleum origin include those referred to asmotor lubricating oil, railroad type lubricating oil, marine oil,transformer oil, turbine oil, transmission oil, differential oil, diesellubricating oil, gear oil, cutting oil, rolling oil, cylinder oil,hydraulic oil, slushing oil, specialty products oil, etc.

The synergistic composition of the present invention serves a number ofimportant functions depending upon the particular lubricant beingstabilized and the conditions under which the lubricant is stored,transported and used. These functions include oxidation inhibitor(peroxide decomposer), color stabilizer, retarding sediment or sludgeformation, dispersion of sediment when formed, bearing corrosioninhibitor, ring antiplugging additive, extreme pressure additive,acidity neutralizer, antibleeding additive, etc.

In one embodiment the present invention relates to the method ofstabilizing a lubricant which comprises incorporating in said lubricanta stabilizing concentration of a synergistic inhibitor composition offrom about 5% to about 95% by weight of a 4,4-diaminodiphenyl ether andfrom about 95% to about 5% by weight of a 2,4-diaminodiphenyl ether.

From the above embodiment, it will be noted that the inhibitorcomposition of the present invention contains both a4,4'-diaminodiphenyl ether and a 2,4'-diaminodiphenyl ether in specifiedproportions. In one embodiment the diaminodiphenyl ethers are free ofsubstitutions on the nitrogen atoms. In another embodiment of thediaminodiphenyl ethers have 1, 2, 3 or 4 hydrocarbon substituentsattached to the nitrogen atom or nitrogen atoms. In still anotherembodiment mixtures of the unsubstituted and of the substituted ormixtures of the differently substituted diaminodiphenyl ethers areemployed. In any case, however, it is required that the 4,4'- and 2,4-diaminodiphenyl ethers be utilized and that these be used in thespecific proportions herein set forth. It is understood that thesesubstituted and unsubstituted diaminodiphenyl ethers are included in thepresent specification and claims in the reference to a4,4'-diaminodiphenyl ether and a 2,4'-diaminodiphenyl ether.

The synergistic effect is obtained when utilizing from about 5% to about95% by weight of a 4,4-diaminodiphenyl ether and from about 95% to about5% by weight of a 2,4'-diaminodiphenyl ether. In a more specificembodiment the inhibitor composition contains from about 20% to about byWeight of a 4,4'-diamino diphenyl ether and from about 80% to about 20%by Weight of a 2,4-diaminodiphenyl ether. 7

It generally is preferred that the substituted diamino- Patented Dec.13, .1961).

diphenyl ethers are N,N'-dialkyI diaminodiphenyl ethers and that thealkyl groups are of secondary or tertiary Configuration and contain from3 to about 12 carbon atoms. Illustrative compositions include mixtureswith in the proportions hereinbefore set forth of the following:N,N'-diisopropyl 4,4'-dlaminodiphenyl ether and N,N'-diisopropyl2,4-diaminodiphenyl ether, N,N'-di-secbutyl 4,4'-diaminodiphenyl etherand N,N'-di-sec-butyl 2,4'-diaminodlphenyl ether, N,N-tert-butyl4,4-diaminodiphenyl ether and N,N'-tert-butyl 2,4-diaminodiphenyl ether,N,N'-sec-amyl 4,4-diaminodiphenyl ether and N,N'-sec-amyl2,4'-diaminodiphenyl ether, N,N-tert-amyl 4,4'-diamino-diphenyl etherand N,N'-tert-amyl 2,4'-diaminodiphenyl ether, N,N-sec-hexyl4,4'-diaminodiphenyl ether and N,N'-sec-hexyl 2,4-diaminodiph'enylether, N,N'-tert-hexyl 4,4'-diaminodiphenyl ether and N,N'-tert-hexyl2,4-diaminodiphenyl ether, N,N'-secheptyl 4,4'-diaminodiphenyl ether andN,N'-sec-heptyl 2,4-diaminodiphenyl ether, N,N-tert-heptyl4,4-diaminodiphenyl ether and N,N'-tert-heptyl 2,4'-diaminodiphenylether, N,N'-sec-octyl 4,4'-diarninodiphenyl ether and N,N'-sec-octyl2,4'-diaminodiphenyl ether, N,N-tertoctyl 4,4'-diaminodiphenyl ether andN,N'-tert-octyl 2,4-diaminodiphenyl ether, etc.

In the specific compounds hereinbefore set forth, the alkyl groups areof the same chain length and configuration. It is understood that, inanother embodiment, the alkyl groups may be different andthe'synergistic composition then will include mixtures'such as thefollowing: N,N'-diisopropyl 4,4'-diaminodiphenyl ether and N,N'-di-sec-butyl 2,4'-diaminodiphenyl ether, N,N'-diisopropyl4,4'-dfaminodiphenyl ether and N,N-di-tert-butyl 2,4- dianiinodiphenylether, N,N'-di-sec-butyl 4,4'-diaminodiphenyl ether andN,N-di-tert-butyl 2,4-diaminodiphenyl ether, etc.,N-isopropyl-N-tert-butyl 4,4-diaminodiphenyl ether andN-isopropyl-N-tert-butyl 2,4-diaminodiphenyl ether, N-sec-amyl4,4-diaminodiphenyl ether, N-sechexyl-N-tert-octyl 2,4'-diaminodiphenylether, etc. 7

While it is preferred that the alkyl groups attached to the nitrogenatoms are of secondary or tertiary configuration, in some cases thealkyl groups may be of primary configuration and are selected frommethyl, ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl,undecyl, dodecyl, etc. In still another embodiment the substitution mayinclude a mixture of the primary and secondary or tertiary alkyl groupsas, for example, compositions comprising a mixture ofN-methyl-N'-isopropyl 4,4- diaminodiphenyl ether andN-methyl-N'-isopropyl 2,4- dlaminodiphenyl ether,N-methyl-N,N-diisopropyl 4,4- diaminodiphenyl ether andN-methyl-N,N-diisopropyl 2,4'-diaminodiphenyl ether,N,N'-dimethyl-N,N-diisopropyl 4,4'-diamniodiphenyl ether andN,N'-dimethyl-N,N'- diisopropyl 2,4'-diaminodiphenyl ether, etc.

From the above description, it will be noted that a number of different4,4'-diaminodiphenyl ethers and 2,4- diaminodiphenyl ethers may be usedin accordance with the present invention. These different mixtures maybe manufactured by separately preparing the 4,4-diaminodiphenyl etherand the 2,4-diaminodiphenyl ether and subsequently mixing them in thedesired proportions, or the mixture of the desired proportions may bemanufactured by utilizing selected reactants in the preparation of thesecompounds. For example, when the composition is prepared by startingwith nitrophenol and nitrochlorobenzene, both para-nitrochlorobenzeneand ortho-nitrochlorobenzene are used in the proportions desired in'thefinal composition. Regardless of the method of preparing or mixing thedifferent components of the composition, it is necessary, ashereinbefore set forth, that both components are present in the finalcomposition and that they are present in the specific proportionshereinbefore set forth.

It is understood that the diiferent compositions which are employed inthe present invention are not necessarily equivalent, but all of themwill exhibit a synergistic effect.

The specific composition to be used will depend upon the availability ofthe reactants and the cost of preparation, as well as upon theparticular lubricant in which the composition is to be used. As anotheradvantage to the composition of the present invention, it may beprepared as a mixture of compounds and will not require separation ofthe individual components of the mixture, but the mixture as produced isused and thus avoids the time and expense which otherwise would berequired in separating individual components.

In general, the inhibitor composition of the present invention isutilized in a concentration of from about 0.001% to about 5% andpreferably of from about 0.01% to about 3% by weight of the lubricant,although in some cases higher or lower concentrations may be employed.

It is understood that the inhibitor composition of the present inventionmay be used along with other additives incorporated in lubricantsincluding, for example, higher alcohols, esters, organic amines,polybutene, sulfurized fatty materials, sulfur chlorine compounds, dyes,fillers, etc. In some cases it may be of advantage to also include ametal deactivator as, for example, disalicylal diaminopropane, etc., orto include other additives such as tricresyl phosphate, dialkylphenols,trialkyl phenols including 2,6-di-tert-butyl-4-methylphenol,2,4-di-methyl-6- tert-butylphenol, alkylated diphenyl amines, phenylnaphthyl amines,'dialkyl phenylene diamines, diarylphenylene diamines,diamino diphenyl methanes, tetraalkyl diaminodiphenyl methanes,diphenylamine, aminophenols, alkylamino phenols, phenothiazine, organicselenium compounds, zlnc dialkyldithiocarbamates, cadmium,dialkyldithiocar-bamates, naphthols, hydroxydiphenylamines,dinaphthyl-p-phenylene diamine-p-phenylene diamine, Nphenyl-N'-cyclohexyl-p-phenylene diamine, reaction prodnets of sulfurdichloride or sulfur monochloride with alkylphenols, aniline,alkylanilines, reaction products of formaldehyde and alkylphenols,guaiacol, etc.

In other cases, especially in lubricating oils, the synergistic mixturemay be used in combination with the following bearing corrosioninhibitors, peroxide decomposers or antioxidants: zinc,dialkyldithiophosphates, phosphorus pentasuIfide-various olefin reactionproducts, sulfur-olefin reaction products, sulfurized terpenes, aromatichydroxysulfides and disul-fides and their neutralization products withcalcium, barium and magnesium oxides or hydroxides, various calcium,barium, magnesium sulfonates, dialkyldithiophosphates, barium or calciumalkylphenates, etc., as well as additional corrosion inhibitors, extremepressure additives, viscosity index improvers, detergents, etc. Whendesired, the inhibitor composition of the present invention may beprepared as a mixture with one or more of these other additives andincorporated in the lubricant in this manner.

The inhibitor composition of the present invention is incorporated inthe lubricant in any suitable manner and at any suitable stage ofpreparation. For example, in the preparation of grease, the inhibitorcomposition may be added to one or more components of the grease priorto compositing or processing thereof or it may be added to the mixtureat any time, preferably before final processing in order to obtainintimate mixing and dissolving of the inhibitor composition in thegrease.

The following examples are introduced to illustrate further the noveltyand utility of the present invention but not with the intention ofunduly limiting the same.

EXAMPLE I The grease used in this example is a lithium base grease andwas prepared by the following general method. Approximately 92% of acommercial Mid-Continent lubricating oil having a S.A.E. viscosity of 20Was mixed with approximately 8% by weight of lithium stearate. Themixture was heated to about 450 F. with constant agitation. Subsequentlythe grease was cooled while ware agitating to 320 F. and at thistemperature the inhibitor in the proper concentration was added.Agitation was continued and the mixture was allowed to cool to about 250F. and the grease then further cooled slowly to room temperature.

The stability of the grease was tested according to ASTM D-942 method,in which method a sample of the grease is placed in a bomb andmaintained at a temperature of 210 F. Oxygen is charged to the bomb, andthe time required for a drop of pounds pressure is taken as theinduction period.

In this set of runs, the inhibitors, when employed, were incorporated inthe grease in a concentration of 0.3% by weight. The first sample ofgrease did not contain an inhibitor and was used as a control. Thesecond sample of grease contained 0.3%"by weight of N,N' diiso-'propyl-2,4'-diaminodiphenyl ether. The third sample of grease contained0.3% by weight of N,N-diisopropyl- 4,4'-diaminodiphenyl ether. The lastsample of grease contained 0.3% by weight of a synergistic mixture ofabout 70% by weight of N,N'-diisopropyl-4,4'-diaminodiphenyl ether andabout 30% by weight of N,N-diisopropyl-2,4-diaminodiphenyl ether. Theresults of these runs are reported in the following table:

From the data in the above table, it will be noted that the mixture ofcompounds exhibited an exceedingly high degree of synergism. Actuallythe run was terminated after 1.873 hours and before a pressure drop of 5pounds was reached. It was apparent that this mixture was soexceptionally synergistic that the stability imparted to the grease wasfar beyond that required for general use. Therefore, it was unnecessaryto continue the run. The pressure drop after 1873 hours was only 3.5pounds.

It will be noted that the 1873 hours far exceeded the expectedstability. Normally it would be expected that the stability would besomewhere between the 830 and 513 hours obtained through the use ofthese compounds individually, more specifically about 600 hours. Incontrast to this expected stability, the stability obtained through theuse of the mixture reached the surprising figure of greater than 1873hours.

EXAMPLE II Another set of runs was made similar to that described inExample I except that 0.1% by weight of the inhib'tor, when employed,was incorporated in the grease. The results of these runs are shown inthe following tabie:

Here again, is seen that the synergistic mixture imparted stability tothe grease far beyond that which would be expected.

EXAMPLE III As hereinbefore set forth, special uses of grease require ahigh degree of stability at higher temperatures. In order to evaluatethe stability of the grease at a higher temperature, the following runswere made with different samples of the grease described in Example Iand in the same manner described therein, except that the temperaturewas 250 F. instead of 210 F. The inhibitors, when employed, wereutilized in a concentration of 0.3% by weight of the grease. The resultsof these runs are shown in the following table:

It is seen that even at this higher temperature, the synergistic mixtureserved to impart a stability to the grease far beyond that expectedthrough the use of each of the compounds singly. As before, it would beexpected that the stability of the grease would be somewhere between the116 hours and 39 hours obtained through the use of each of thesecompounds separately, more specifically about hours. In contrast, theactual stabiiiy obtained through the use of the synergistic mixture isthe surprisingly high period of 362 hours.

EXAMPLE IV This example reports results using djiferent mixtures of theinhibitor compounds described in Example III and shows that thesynergistic effect prevails in all these mixtures. These runs were madeusing dilIerent samples of the grease and in the same manner asdescribed in Example III, and 0.3% by weight of the ditferent inhibitormixtures. The results of these runs are shown in the following table:

Table IV Percent by Percent by Induction weight of weight of PeriodNumber N,N-diisopro- N,N-cliis"pro- (Hams to pyl-2,4'-diarnipyl4,4-diami5 pounds nooiphenyl nodipbenyl pressure ether ether drop) Here again, itwill be noted that the mixture is synergistic throughout the rangesshown in the table. These results are to be compared with those ofcompounds 10 and 11 shown in Table III. This particular set of runs didnot include compositions containing 5% of one of the compounds and ofthe other, but other runs have shown that the synergistic effect alsoprevails.

through these ranges. It will be noted that synergistic mixture 15 isthe same as synergistic mixture 12 reported in Table III and also thatin this particular set of runs this mixture appears to be somewhatbetter than the other mixtures. It is understood that the variousmixtures will not necessarily be equivalent in the same or difierentlubricants but that all of the mixtures withinthe proportions specifiedherein will exhibit a synergistic effect.

EXAMPLE V This example reports runs made in a lithium base greaseprepared with a different commercial Mid-Continent lubricating oilof'S.A.E. 20. The lithium base grease was prepared in substantially thesame manner described in Example I except for the dilierent oil, and wasevaluated at 250 F. This different grease had a control (no inhibitor)stability of 4 hours, whereas the grease used in Examples I and II had acontrol stability of 2 hours.

In these runs the unsubstituted diaminodiphenyl ethers were utilized.The results of these evaluations are reported in the following table:

Table V Induction Number Inhibitor Period (Hours to 5 pounds pressuredrop) 19. None 4 20 2,4-diaininodiphenyl ether 121 214,4-diarninodiphenyl ether 142 22 Synergistic mixture of about 70% ofcorn- 224 pound No. 21 and about 30% of compound N o. 20.

Here again, it will be noted that the mxture exerted a synergisticeffect. As before, it would be expected that the stability imparted tothe grease would be between 121 hours and 142 hours" which were obtainedwith the compounds singly, more specifically about 136 hours. Incontrast, the synergistic mixture imparted a stability to the grease of224 hours.

EXAMPLE V I This example illustrates the use of the synergistic mixtureof the present invention in a calcium base grease, which is prepared bythe following general method. The calcium soap is prepared by mixing thefat, hydrated lime equivalent to about one-seventh of the fat, mineraloil sufiicient to make about one-fourth of the total charge, and about0.5% of water. The ingredients are mixed and heated to about 140 F. andthen dry lime is added, agitation and heat continued untilsaponification is completed. Additional oil then is added and themixture heated to 220230 -F. Additional oil' is added to bring themixture to the desired consistency, and then is heated at 170180 F. Atthis point, 0.02% by weight of a synergistic mixture of about 80% byweight of N,N'-disec-butyl 4,4'-diaminodiphenyl ether and about 20% byweight of N,N'-di-sec-butyl. 2,4'-diaminodiphenyl ether, along withother additives, is added, and the mixing is continued until formationof grease of the desired structure.

EXAMPLE VII This example illustrates the use of the synergistic mixtureof the present invention in a motor lubricating oil of petroleum origin.These runs were conducted in a Lauson engine, using a jacket temperatureof 210 F. and an oil temperature of 280 F. A commercial lubricating oilof S.A.E. '20 viscosity was used and the runs were continued. for 115hours. Pertinent results of these runs, using a sample of'thelubricating oil which did not contain an inhibitor, and a differentsample of the same oil containing 0.5% by weight of a synergisticmixture of about 70% by weight of N,N'-diisopropyl 2,4'-diaminodiphenylether and about 30% by weight of N,N-diiso- 8. propyl4,4-dian:1inodiphenyl ether following table:

are reported in the Referring to the data in the above table, it will benoted that the synergistic mixture of the present invention served toconsiderably reduce bearing weight loss,

which illustrates the corrosion inhibiting and acidity neutralizingproperties of the synergistic mixture. It also will' be noted that theused oil neutralization number is considerably lower, thus illustratingthe antioxidant or peroxide decomposing properties of the synergisticmixture. The lower viscosities of the used oil containing thesynergistic mixture illustrate the effectiveness of the mixture toinhibit formation of heavier products.

EXAMPLE VIII This example illustrates the use of the synergistic mixtureof the present invention in a synthetic lubricant. The effectiveness ofthe synergistic mixture was determined in an accelerated test in which asample of the synthetic lubricant is placed in a glass test cell fittedwith a condenser and a gas delivery tube extending through the top tonear the bottom of the test cell. The test cell is immersed in an oilbath to maintain a temperature of 204 C. Air is passed through the cellat a rate of 5 liters of air per hour. Samples of the lubricant arewithdrawn periodically for analysis. The induction period is taken asthe number of hours required to reach an acid number of 5.

The synthetic lubricant used in this example is di-(2- ethylhexyl)sebacate. The synergistic mixture used in this example contained about70% by weight of N,N-

dii-sopropyl 2,4-diaminodiphenyl ether and about 30% by weight ofN,N'-diisopropyl 4,4'-diaminodiphenyl ether.

When evaluated in the above manner, the control sample (not containinginhibitor) reached the induction period in 12 hours. On the other hand,the sample of synthetic lubricant containing the synergistic mixture didnot reach the induction period until 50.hours. Thus, it will. be seenthat the synergistic mixture etfectively' stabilized the syntheticlubricant.

I claim as my invention:

1. A synergistic inhibitor mixture of from about 5% to about by weightof a 4,4-diaminodiphenyl ether and from about 95% to about. 5% by weightof a 2,4- diaminodiphenyl ether.

2. A synergistic inhibitor mixture of from about 5% to about95% ofN,N"-diisopropyl 4,4'-diaminodiphenyl ether and from about 95 to about5% by weight of I I,N'-diisopropyl '2,4"-diaminodiphenyl ether.

3; A synergistic inhibitor mixture of from about 5% to about 95 ofN,N'-di-sec-butyl 4,4-diarninodiphenyl ether and from about 95 to about5% by weight of N,N'-di-sec-butyl 2,4'-diaininodiphenyl ether.

References Cited in the file of this patent UNITED STATES PATENTS

1. A SYNERGISTIC INHIBITOR MIXTURE OF FROM ABOUT 5% TO ABOUT 95% BYWEIGHT OF A 4,4''-DIAMINODIPHENYL ETHER AND FROM ABOUT 95% TO ABOUT 5%BY WEIGHT OF A 2,4''DIAMINODIPHENYL ETHER.